This invention relates to delivery systems or apparatus for the production and distribution of liquids droplets by means of an electromechanical transducer. A number of processes exist for the generation of droplets using electromechanical actuation. One method for such distribution is to atomize a liquid by a device comprising a membrane which is vibrated by an electromechanical transducer which has a composite thin-walled structure, and is arranged to operate in a bending mode. Liquid is supplied directly to a surface of the membrane and sprayed therefrom in fine droplets upon vibration of the membrane. An example of such a method is shown by Humberstone et al, in U.S. Pat. No. 5,518,179.
Another atomizer spraying device is described by Toda, U.S. Pat. No. 5,297,734. This application teaches the use of ultrasonic atomizing devices comprising piezoelectric vibrators with a vibrating plate connected thereto. The vibrating plate is described as having a large number of small holes therein for passage of the liquid.
Another electromechanical atomizer spraying device is shown by Martin et al, in U.S. Pat. No. 6,341,732, this device allows fluid to be withdrawn from a reservoir to be atomized effectively and continuously without liquid build-up on the atomizing element by allowing the fluid to flow back to the reservoir without spilling or waste.
In yet another electromechanical atomization system, Martens III et al, U.S. Pat. No. 6,378,780, described a battery operated device that can be used to automatically dispense liquids to any given environment, over an extended period of time, with the advantage of uniformly dispensing equal amounts of liquid to the atmosphere over the life span of the battery. The accuracy in dispensing rate is claimed to translate into consistency with respect to perfume character and intensity. In addition, the amount of liquid being dispersed may be varied to adjust intensity for personal preference, efficacy, or for room size. This system also claimed that the life of the power source is lengthened by control of the viscosity and surface tension of the liquid to be dispensed to within specified ranges.
U.S. Pat. No. 6,712,287, assigned to Osmooze, relates to a piezoelectric element fastened to a delivery needle to generate droplets that are then diffusion assisted by a mechanical device or air pump to reduce habituation. However, the use of a needle as droplet generation element is limited when compare with a perforated plate, because the needle does not provide any physical element to control droplet particle size. In this application, the droplet size is determined by the surface tension and viscosity of the formulation, significantly reducing the performance and fields of application of the design. Droplets generated in this manner are typically in the range of 20 to 50 microns, too large to be supported or carried by typical air currents and not suited for air freshener applications even with the use of assisted air flow devices. In addition, droplets of the size generated by this device will require higher air flow volumes to stay airborne. Attempts to decrease the diameter of the needle significantly increase the work load on the piezoelectric element and thus power consumption.
While there are a significant number patents that disclose means for the dispersion of liquids by ultrasonic atomization using given time intervals, or viscosity or surface tension ranges, they have achieved only moderate success in the efficient atomization and dispersion of the liquid droplets to deliver acceptable room fill with a balanced composition. This is of greater importance with complex materials such as perfume formulations. See, for example, U.S. Pat. Nos. 3,543,122, 3,615,041, 4,479,609, 4,533,082, and 4,790,479. The disclosures of these patents, and of all other publications referred to herein, are incorporated by reference as if fully set forth herein.
These atomizer systems fail to provide an electromechanical atomization system capable of delivering complex perfume formulations for extended periods of use that provide consistency with respect to intended character, intensity and emission rate. Further, these systems fail to deliver wide dispersal of the fluid in an energy efficient manner, resulting in a device that does not deliver acceptable and user-preferred room fill. It is even more challenging to deliver such a benefit in an easily portable and compact battery operated dispenser. Thus, a need exists for improved atomizers or dispensers for use in the delivery and distribution of active fluids such as fragrances and other volatile ingredients, in a highly efficient manner consuming minimal electrical power while providing wide dispersal of the liquid.